ApoE have been isolated in electrophoretically homogeneous form from normal subjects and patients with Type III and V hyperlipidemia. ApoE from Type III patients was missing the E3 isoform on isoelectric focusing, however on 2 dimensional electrophoresis the entire protein appeared shifted in pI. ApoE from all sources had identical amino acid compositions, however metabolic studies have shown that Type IIIE was functionally abnormal when compared to normal apoE. ApoH has been isolated to electrophoretic homogeneity from lipoproteins of thoracic duct lymph and the chylo-VLDL fraction (d less than 1.006 g/ml) of normal and Type V subjects. ApoH was shown to be structural identical to beta 2-glycoprotein-I. ApoH was shown to activated post heparin lipoprotein lipase, and is proposed to have an important role in triglyceride metabolism. ApoB has been recognized to exist in man in two distinct electrophoretic forms varying in apparent molecular weight on SDS gel electrophoresis. The larger and smaller apoB have been proposed to be of liver and intestinal origin respectively.